Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$181.37	6.345%	$192.8779	$192.88	$192.90	$192.90
Purchase #2	$53.68	10.113%	$59.1087	$59.11	$59.10	$59.10
Purchase #3	$135.43	7.410%	$145.4654	$145.47	$145.45	$145.50
Purchase #4	$144.25	5.790%	$152.6021	$152.60	$152.60	$152.60
Purchase #5	$115.55	3.341%	$119.4105	$119.41	$119.40	$119.40
Purchase #6	$200.28	12.622%	$225.5593	$225.56	$225.55	$225.60
Purchase #7	$115.33	8.479%	$125.1088	$125.11	$125.10	$125.10
7 purchase totals =	$945.89		$1,020.1327	$1,020.14	$1,020.10	$1,020.20